Laser-processing of features (e.g., through-vias, blind vias, trenches, routs, kerfs, and other features) within one or more materials of a workpiece can be sensitive to laser power. In many applications (e.g., in which features are laser-processed by delivering laser pulses onto the workpiece), the speed or efficiency with which a feature is formed, and the quality of the feature ultimately formed, can be very sensitive to the pulse energy of the individual pulses delivered to the workpiece. For example, when laser-processing a workpiece such as a printed circuit board, a flexible printed circuit, or the like, a relatively high pulse energy may be desirable when laser processing (e.g., ablating) an electrically conductive material such as copper, while a relatively lower pulse energy may be desirable when laser processing (e.g., ablating) a dielectric material without inducing heat effects (e.g., due to charring and/or melting) within the dielectric material and without damaging adjacent materials (e.g., copper).
Conventional methods of controlling or adjusting laser power or pulse energy include attenuation optics (e.g., polarization optics or acousto-optic modulators), or direct control of laser optical output power by varying the pump power to the lasing medium. These conventional approaches have disadvantages including slow speed (e.g., for mechanically-adjusted polarization optics), variation in laser delivery (e.g., in the control of lasing medium pumping or Q-switch timing), or a lack of coordination with other operations of the laser processing apparatus.